text: The mathematical explanation for the positive bias in the calculation of work using the resting ocean wind stress can also be interpreted physically through the mechanical damping effect. As seen in Figure 2, when the wind velocity and ocean current velocity are in the same direction, the relative wind stress is smaller than the resting ocean wind stress. In other words, less positive work is using relative wind stress. When the wind and the ocean velocities are in opposite directions, then the relative wind stress does more negative work than the resting ocean wind stress. Consequently, in both scenarios less work is being done on the ocean when the relative wind stress is used for the calculation. 
  This physical interpretation can also be adapted to a scenario where there is an ocean eddy. As illustrated on the top part of Figure 3, in the eddy situation, the relative wind stress is smaller when the wind and ocean velocities are aligned, a similar situation to the top part of Figure 2. At the bottom part of Figure 3 we have a situation analogous to the bottom part of Figure 2, where more negative work is being performed on the system than in the resting ocean case. Therefore, at the top of the eddy less energy is being put in and at the bottom more energy is being taken out, which means the eddy is being dampened more in the relative wind case. 
  The two situations depicted in Figures 2 and 3 are the physical reason why there is a positive bias when estimating the power (work per unit time) input to the ocean when using the resting ocean stress rather than the relative wind stress .